Ring Off/On Bolt and Nut

The magician shows a large brass bolt and nut. He asks for a ring, or offers one of his own for inspection. Showing his hands empty, he puts the ring underneath a handkerchief and moves the handkerchief over bolt and nut. Instantly he removes the handkerchief and the rings on the bolt between the nut and the closed end of the bolt. The nut is half-way along the bolt and it would take a lot of time to unscrew the nut, put the ring on, then screw the nut back on the bolt. Yet the magician has done it in a flash. Includes instructions. Very good condition.